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  • richardmitnick 10:59 am on February 22, 2019 Permalink | Reply
    Tags: , LLC, Nuclear power scheme-Twelve-pack of power. C. BICKEL/SCIENCE, NUSCALE POWER, , Science Magazine   

    From Science Magazine: “Smaller, safer, cheaper: One company aims to reinvent the nuclear reactor and save a warming planet” 

    AAAS
    From Science Magazine

    Feb. 21, 2019
    Adrian Cho

    1
    NuScale researchers want to operate 12 small nuclear reactors from a single control room. They built a mock one in Corvallis, Oregon, to show they can do it.
    NUSCALE POWER, LLC

    To a world facing the existential threat of global warming, nuclear power would appear to be a lifeline. Advocates say nuclear reactors, compact and able to deliver steady, carbon-free power, are ideal replacements for fossil fuels and a way to slash greenhouse gas emissions. However, in most of the world, the nuclear industry is in retreat. The public continues to distrust it, especially after three reactors melted down in a 2011 accident at the Fukushima Daiichi Nuclear Power Plant in Japan. Nations also continue to dither over what to do with radioactive reactor waste. Most important, with new reactors costing $7 billion or more, the nuclear industry struggles to compete with cheaper forms of energy, such as natural gas. So even as global temperatures break one record after another, just one nuclear reactor has turned on in the United States in the past 20 years. Globally, nuclear power supplies just 11% of electrical power, down from a high of 17.6% in 1996.

    Jose Reyes, a nuclear engineer and cofounder of NuScale Power, headquartered in Portland, Oregon, says he and his colleagues can revive nuclear by thinking small. Reyes and NuScale’s 350 employees have designed a small modular reactor (SMR) that would take up 1% of the space of a conventional reactor. Whereas a typical commercial reactor cranks out a gigawatt of power, each NuScale SMR would generate just 60 megawatts. For about $3 billion, NuScale would stack up to 12 SMRs side by side, like beer cans in a six-pack, to form a power plant.

    But size alone isn’t a panacea. “If I just scale down a large reactor, I’ll lose, no doubt,” says Reyes, 63, a soft-spoken native of New York City and son of Honduran and Dominican immigrants. To make their reactors safer, NuScale engineers have simplified them, eliminating pumps, valves, and other moving parts while adding safeguards in a design they say would be virtually impervious to meltdown. To make their reactors cheaper, the engineers plan to fabricate them whole in a factory instead of assembling them at a construction site, cutting costs enough to compete with other forms of energy.

    Spun out of nearby Oregon State University (OSU) here in 2007, NuScale has spent more than $800 million on its design—$288 million from the Department of Energy (DOE) and the rest mainly from NuScale’s backer, the global engineering and construction firm Fluor.

    The design is now working its way through licensing with the Nuclear Regulatory Commission (NRC), and the company has lined up a first customer, a utility association that wants to start construction on a plant in Idaho in 2023.

    NuScale is far from alone. With similar projects rising in China and Russia, the company is riding a global wave of interest in SMRs. “SMRs as a class have a potential to change the economics,” says Robert Rosner, a physicist at the University of Chicago in Illinois who co-wrote a 2011 report on them. In the United States, NuScale is the only company seeking to license and build an SMR. Rosner is optimistic about its prospects. “NuScale has really made the case that they’ll be able to pull it off,” Rosner says.

    For now, NuScale’s reactors exist mostly as computer models. But in an industrial area north of town here, the company has built a full-size mock-up of the upper portion of a reactor. Festooned with pipes, the 8-meter-tall gray cylinder isn’t exactly small. It resembles the conning tower of a submarine, one that has somehow surfaced through the dusty ground. NuScale built it to see if workers could squeeze inside for inspections, says Ben Heald, a NuScale reactor designer. “It’s a great marketing tool.”

    Not everyone thinks NuScale will make the transition from mock-up to reality, however. Dozens of advanced reactor designs have come and gone. And even if NuScale and other startups succeed, the nuclear industry won’t build enough plants quickly enough to matter in the fight against climate change, says Allison Macfarlane, a professor of public policy and geologist at George Washington University in Washington, D.C., who chaired NRC from 2012 through 2014. “Nuclear does not do anything quickly,” she says.

    Nuclear power scheme-Twelve-pack of power. C. BICKEL/SCIENCE

    A nuclear reactor is a glorified boiler. Within its core hang ranks of fuel rods, usually filled with pellets of uranium oxide. The radioactive uranium atoms spontaneously split, releasing energy and neutrons that go on to split more uranium atoms in a chain reaction called fission. Heat from the chain reaction ultimately boils water to drive steam turbines and generate electricity.

    Designs vary, but 85% of the world’s 452 power reactors circulate water through the core to cool it and ferry heat to a steam generator that drives a turbine.

    The water plays a second safety role. Power reactors typically use a fuel with a small amount of the fissile isotope uranium-235. The dilute fuel sustains a chain reaction only if the neutrons are slowed to increase the probability that they’ll split other atoms. The cooling water itself serves to slow, or moderate, the neutrons. If that water is lost in an accident, fission fizzles, preventing a runaway chain reaction like the one that blew up a graphite-moderated reactor in 1986 at the Chernobyl Nuclear Power Plant in Ukraine.

    Even after the chain reaction dies, however, heat from the radioactive decay of nuclei created by fission can melt the core. That happened at Fukushima when a tsunami swamped the emergency generators needed to pump water through the plant’s reactors.

    NuScale’s design would reduce such risks in multiple ways. First, in an accident the small cores would produce far less decay heat. NuScale engineers have also cut out the pumps that drive the cooling water through the core, relying instead on natural convection. That design eliminates moving parts that could fail and cause an accident in the first place, says Eric Young, a NuScale engineer. “If it’s not there, it can’t break,” he says.

    NuScale’s new reactor housings offer further protection. A conventional reactor sits within a reinforced concrete containment vessel up to 40 meters in diameter. Each 3-meter-wide NuScale reactor nestles into its own 4.6-meter-wide steel containment vessel, which by virtue of its much smaller diameter can withstand pressures 15 times greater. The vessels sit submerged in a vast pool of water: NuScale’s ultimate line of defense.

    For example, in an emergency, operators can cool the core by diverting steam from the turbines to heat exchangers in the pool. During normal operations, the space between the reactor and the containment vessel is kept under vacuum, like a thermos, to insulate the core and allow it to heat up. But if the reactor overheats, relief valves would pop open to release steam and water into the vacuum space, where they would transfer heat to the pool. Such passive features ensure that in just about any conceivable accident, the core would remain intact, Reyes says.

    To prove that the reactor will behave as predicted, NuScale engineers have constructed a one-third scale model. A 7-meter tall tangle of pipes, valves, and wires lurks in the corner of a lab at OSU’s department of nuclear engineering. The model aims not to run exactly like the real reactor, Young says, but rather to validate the computer models that NRC will use to evaluate the design’s safety. The model’s core heats water not with nuclear fuel but with 56 electric heaters like those in curling irons, Young says. “It’s like a big percolator,” he says. “We set up a test and watch coffee being made for 3 days.”

    Making a reactor smaller has a downside, says M. V. Ramana, a physicist at the University of British Columbia in Vancouver, Canada. A smaller reactor will extract less energy from every ton of fuel, he argues, driving up operating costs. “There’s a reason reactors became larger,” Ramana says. “Inherently, NuScale is giving up the advantages of economies of scale.”

    But small size pays off in versatility, Reyes says. One little reactor might power a plant to desalinate seawater or supply heat for an industrial process. A customized NuScale plant might support a developing country’s smaller electrical grid. And in the developed world, where intermittent renewable sources are growing rapidly, a full 12-pack of reactors could provide steady power to make up for the fitful output of windmills and solar panels. By varying the number of reactors producing power, a NuScale plant could “load follow” and fill in the gaps, Reyes says.

    See the full article here .


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  • richardmitnick 10:34 am on February 22, 2019 Permalink | Reply
    Tags: "Did volcanic eruptions help kill off the dinosaurs?", A large impact crater in the Gulf of Mexico, A massive asteroid strike 66 million years ago that unleashed towering tsunamis and blotted out the sun with ash causing a plunge in global temperatures, Across what is India today countless volcanic seams opened in the ground releasing a flood of lava resembling last year’s eruptions in Hawaii—except across an area the size of Texas, , Over the course of 1 million years the greenhouse gases from these eruptions could have raised global temperatures and poisoned the oceans leaving life in a perilous state before the asteroid impact, Science Magazine, Some 400000 years before the impact the planet gradually warmed by some 5°C only to plunge in temperature right before the mass extinction, The Deccan Traps,   

    From Science Magazine: “Did volcanic eruptions help kill off the dinosaurs?” 

    AAAS
    From Science Magazine

    Feb. 21, 2019
    Paul Voosen

    1
    The hardened lava flows of the Deccan Traps, in western India, may have played a role in the demise of the dinosaurs. Gerta Keller

    What killed off the dinosaurs? The answer has seemed relatively simple since the discovery a few decades ago of a large impact crater in the Gulf of Mexico. It pointed to a massive asteroid strike 66 million years ago that unleashed towering tsunamis and blotted out the sun with ash, causing a plunge in global temperatures.

    But the asteroid wasn’t the only catastrophe to wallop the planet around this time. Across what is India today, countless volcanic seams opened in the ground, releasing a flood of lava resembling last year’s eruptions in Hawaii—except across an area the size of Texas. Over the course of 1 million years, the greenhouse gases from these eruptions could have raised global temperatures and poisoned the oceans, leaving life in a perilous state before the asteroid impact.

    The timing of these eruptions, called the Deccan Traps, has remained uncertain, however. And scientists such as Princeton University’s Gerta Keller have acrimoniously debated [Science] how much of a role they played in wiping out 60% of all the animal and plant species on Earth, including most of the dinosaurs.

    That debate won’t end today. But two studies published in Science have provided the most precise dates for the eruptions so far—and the best evidence yet that the Deccan Traps may have played some role in the dinosaurs’ demise.

    There’s long been evidence that Earth’s climate was changing before the asteroid hit. Some 400,000 years before the impact, the planet gradually warmed by some 5°C, only to plunge in temperature right before the mass extinction. Some thought the Deccan Traps could be responsible for this warming, suggesting 80% of the lava had erupted before the impact.

    But the new studies counter that old view. In one, Courtney Sprain, a geochronologist at the University of Liverpool in the United Kingdom, and colleagues took three trips to India’s Western Ghats, home of some of the thickest lava deposits from the Deccan Traps. They sampled various basaltic rocks formed by the cooled lava. The technique they used, called argon-argon dating, dates the basalt’s formation, giving a direct sense of the eruptions’ timing.

    The researchers’ dates suggest the eruptions began 400,000 years before the impact, and kicked into high gear afterward, releasing 75% of their total volume [Science]in the 600,000 years after the asteroid strike. If the Deccan Traps had kicked off global warming, their carbon dioxide (CO2) emissions had to come before the lava flows really got going—which, Sprain adds, is plausible, given how much CO2 scientists see leaking from modern volcanoes, even when they’re not erupting.

    The dates, and the increase in lava volume after the impact, also line up with a previous suggestion by Sprain’s team, including her former adviser, Paul Renne, a geochronologist at the University of California, Berkeley, that the two events are directly related: The impact might have struck the planet so hard that it sent the Deccan Traps into eruptive high gear [Science].

    The second study used a different method to date the eruptions. A team including Keller and led by Blair Schoene, a geochronologist at Princeton, looked at zircon crystals [Science] trapped between layers of basalt. These zircons can be precisely dated using the decay of uranium to lead, providing time stamps for the layers bracketing the eruptions. The zircons are also rare: It was a full-time job, lasting several years, to sift them out from the rocks at the 140 sites they sampled.

    The dates recovered from the crystals suggest that the Deccan Traps erupted in four intense pulses [Science] rather than continuously, as Sprain suggests. One pulse occurred right before the asteroid strike. That suggests the impact did not trigger the eruptions, he says. Instead, it’s possible this big volcanic pulse before the asteroid impact did play a role in the extinction, Schoene says. “It’s very tempting to say.” But, he adds, there’s never been a clear idea of how exactly these eruptions could directly cause such extinctions.

    Though the two studies differ, they largely agree on the overall timing of the Deccan eruptions, Schoene says. “If you plot the data sets over each other, there’s almost perfect agreement.”

    This match represents a victory, says Noah McLean, a geochemist at the University of Kansas in Lawrence, who was not involved in either study. For decades, dates produced with these geochronological techniques couldn’t line up. But improved techniques and calibration, McLean says, “helped us go from million-year uncertainties to tight chronologies.”

    Solving the mystery of how the dinosaurs died isn’t just an academic problem. Understanding how the eruptions’ injection of CO2 into the atmosphere changed the planet is vital not only for our curiosity about the dinosaurs’ end, but also as an analog for today, Sprain says. “This is the most recent mass extinction we have,” Sprain says. Teasing apart the roles of the impact and the Deccan Traps, she says, can potentially help us understand where we’re heading.

    See the full article here .


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  • richardmitnick 11:20 am on February 15, 2019 Permalink | Reply
    Tags: "Physicists create a quantum refrigerator that cools with an absence of light", , , , Near-field photonic cooling through control of the chemical potential of photons, , , Science Magazine,   

    From U Michigan via Science Magazine: “Physicists create a quantum refrigerator that cools with an absence of light” 

    U Michigan bloc

    From University of Michigan

    via

    AAAS
    Science Magazine

    Feb. 14, 2019
    Daniel Garisto

    1
    This new device shows that an LED can cool other tiny objects. Joseph Xu/Michigan Engineering, Communications & Marketing

    For decades, atomic physicists have used laser light to slow atoms zinging around in a gas, cooling them to just above absolute zero to study their weird quantum properties. Now, a team of scientists has managed to similarly cool an object—but with the absence of light rather than its presence. The technique, which has never before been experimentally shown, might someday be used to chill the components in microelectronics.

    In an ordinary laser cooling experiment, physicists shine laser light from opposite directions—up, down, left, right, front, back—on a puff of gas such as rubidium. They tune the lasers precisely, so that if an atom moves toward one of them, it absorbs a photon and gets a gentle push back toward the center. Set it up just right and the light saps away the atoms’ kinetic energy, cooling the gas to a very low temperature.

    But Pramod Reddy, an applied physicist at the University of Michigan in Ann Arbor, wanted to try cooling without the special properties of laser light. He and colleagues started with a widget made of semiconducting material commonly found in video screens—a light-emitting diode (LED). An LED exploits a quantum mechanical effect to turn electrical energy into light. Roughly speaking, the LED acts like a little ramp for electrons. Apply a voltage in the right direction and it pushes electrons up and over the ramp, like kids on skateboards. As electrons fall over the ramp to a lower energy state, they emit photons.

    Crucially for the experiment, the LED emits no light when the voltage is reversed, as the electrons cannot go over the ramp in the opposite direction. In fact, reversing the voltage also suppresses the device’s infrared radiation—the broad spectrum of light (including heat) that you see when you look at a hot object through night vision goggles.

    That effectively makes the device colder—and it means the little thing can work like a microscopic refrigerator, Reddy says. All that’s necessary is to put it close enough to another tiny object, he says. “If you take a hot object and a cold object … you can have a radiative exchange of heat,” Reddy says. To prove that they could use an LED to cool, the scientists placed one just tens of nanometers—the width of a couple hundred atoms—away from a heat-measuring device called a calorimeter. That was close enough to increase the transfer of photons between the two objects, due to a process called quantum tunneling. Essentially, the gap was so small that photons could sometimes hop over it.

    The cooler LED absorbed more photons from the calorimeter than it gave back to it, wicking heat away from the calorimeter and lowering its temperature by a ten-thousandth of a degree Celsius, Reddy and colleagues report this week in Nature. That’s a small change, but given the tiny size of the LED, it equals an energy flux of 6 watts per square meter. For comparison, the sun provides about 1000 watts per square meter. Reddy and his colleagues believe they could someday increase the cooling flux up to that strength by reducing the gap size and siphoning away the heat that builds up in the LED.

    The technique probably won’t replace traditional refrigeration techniques or be able to cool materials below temperatures of about 60 K. But it has the potential to someday be used for cooling microelectronics, according to Shanhui Fan, a theoretical physicist at Stanford University in Palo Alto, California, who was not involved with the work. In earlier work, Fan used computer modeling to predict that an LED could have a sizeable cooling effect if placed nanometers from another object. Now, he said, Reddy and his team have realized that idea experimentally.

    See the full article here .


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    U MIchigan Campus

    The University of Michigan (U-M, UM, UMich, or U of M), frequently referred to simply as Michigan, is a public research university located in Ann Arbor, Michigan, United States. Originally, founded in 1817 in Detroit as the Catholepistemiad, or University of Michigania, 20 years before the Michigan Territory officially became a state, the University of Michigan is the state’s oldest university. The university moved to Ann Arbor in 1837 onto 40 acres (16 ha) of what is now known as Central Campus. Since its establishment in Ann Arbor, the university campus has expanded to include more than 584 major buildings with a combined area of more than 34 million gross square feet (781 acres or 3.16 km²), and has two satellite campuses located in Flint and Dearborn. The University was one of the founding members of the Association of American Universities.

    Considered one of the foremost research universities in the United States,[7] the university has very high research activity and its comprehensive graduate program offers doctoral degrees in the humanities, social sciences, and STEM fields (Science, Technology, Engineering and Mathematics) as well as professional degrees in business, medicine, law, pharmacy, nursing, social work and dentistry. Michigan’s body of living alumni (as of 2012) comprises more than 500,000. Besides academic life, Michigan’s athletic teams compete in Division I of the NCAA and are collectively known as the Wolverines. They are members of the Big Ten Conference.

     
  • richardmitnick 11:46 am on February 7, 2019 Permalink | Reply
    Tags: A costly and controversial space-based cosmic ray detector has found possible signs of dark matter, AMS began to measure the mass charge and energy of the billions of cosmic rays—charged particles from space—that pass down its maw, , , , , Officials in DOE's high energy physics program which funds the AMS's $4.5 million operating budget held a review to rank 13 ongoing projects. The AMS tied for last. The problem lay not with the experi, Positrons could come from the interactions of cosmic rays themselves, Samuel Ting a particle physicist at the Massachusetts Institute of Technology, Science Magazine, The AMS paper acknowledges that dark matter annihilation is just one possible explanation for the positrons, The space-based Alpha Magnetic Spectrometer on the ISS, Ting is also holding out for a different jaw-dropping discovery: heavy antimatter nuclei   

    From Science Magazine: “Space magnet homes in on clue to dark matter” 

    AAAS
    From Science Magazine

    Feb. 6, 2019
    Adrian Cho

    CERN Alpha Magnetic Spectrometer

    The space-based Alpha Magnetic Spectrometer on the ISS

    A costly and controversial space-based cosmic ray detector has found possible signs of dark matter, the invisible stuff thought to supply most of the universe’s mass. Or so says Samuel Ting, a particle physicist at the Massachusetts Institute of Technology in Cambridge and leader of the Alpha Magnetic Spectrometer (AMS), which is perched on the International Space Station (ISS).

    However, time is running out for the aging detector, and many researchers are skeptical about the dark matter interpretation, which Ting dances around with typical coyness. “If you listen to the storyline, it does sound like that’s where we’re headed, but we never quite get there,” says Angela Olinto, a cosmic ray physicist at the University of Chicago in Illinois.

    The co-winner of the 1976 Nobel Prize in Physics, Ting, 83, jetted around the world to drum up $1.5 billion for the AMS, and wooed NASA and the Department of Energy (DOE) into backing it. After astronauts bolted the 8500-kilogram, doughnut-shaped detector to the ISS in May 2011, it began to measure the mass, charge, and energy of the billions of cosmic rays—charged particles from space—that pass down its maw. Almost all of them are protons, electrons, and light nuclei such as helium, but a precious few consist of antimatter particles such as positrons. They stand out because, in the magnetic field of the AMS, their paths bend in the opposite direction from those of their matter counterparts.

    In 2014, AMS researchers reported an unexpected flux of positrons that kicked in at energies above 10 giga-electron volts (GeV) and seemed to fade by about 300 GeV. The excess could come from dark matter particles colliding and annihilating one another to produce electron-positron pairs, and the energy of the falloff might point to the mass of the dark matter particles. Now, with three times as many data, AMS researchers have clearly resolved that energy cutoff. The positron excess starts at 25 GeV and falls sharply at 284 GeV, the 227-member AMS team reported last week in Physical Review Letters. “It’s important because you do start to see a turnaround” in the energy spectrum, Olinto says. The cutoff is consistent with heavy dark matter particles with a mass of about 800 GeV, the researchers report.

    The AMS paper acknowledges that dark matter annihilation is just one possible explanation for the positrons. They could also come from a mundane astrophysical object, such as a pulsar—a spinning neutron star. But Ting emphasizes the steepness of the cutoff. “The cutoff also goes very quickly, very similar to [the signal from] dark matter collisions,” he says.

    In a third possibility, the positrons could come from the interactions of cosmic rays themselves. Cosmic ray protons emerging from remnants of supernova explosions regularly slam into atomic nuclei in interstellar space to create “secondary” cosmic rays, including positrons. AMS researchers say they’ve ruled out that explanation for the signal, because the proton collisions should produce a long tail in the positron spectrum instead of a sharp falloff. But Greg Tarlé, a cosmic ray physicist at the University of Michigan in Ann Arbor, says the AMS data reveal a telltale similarity between the energy spectrum of the positrons and that of the protons, supporting the idea that the protons are the source. “It’s the AMS data itself that give the best evidence for the positrons being secondaries,” Tarlé says.

    Every explanation for the positron excess has significant problems, cosmic ray experts say, but Ting insists the AMS may still sort it all out. The detector could run for the remaining life span of the ISS, perhaps until 2024. The AMS team will then have twice as many data, enough to tell whether the positron spectrum dives as steeply as dark matter scenarios predict, Ting says. Stephane Coutu, a physicist at Pennsylvania State University in University Park, disagrees. Doubling the data will shrink the error bars just 30%, he says, too little to resolve the issue. “They’re basically done,” Coutu says. “The rest is gilding a lily.”

    In May 2018, a federal advisory panel reached a similar conclusion. In 2017, the White House proposed slashing DOE’s research budget by 17%. In response, officials in DOE’s high energy physics program, which funds the AMS’s $4.5 million operating budget, held a review to rank 13 ongoing projects. The AMS tied for last. The problem lay not with the experiment, but with the theories to interpret its data, says Paul Grannis, a physicist at the State University of New York in Stony Brook who led the review. The theoretical uncertainties are “so big that anything you could do to improve the data will have very little impact,” Grannis says. In the end, Congress boosted the 2018 high energy physics budget by 10%, and DOE officials say they have no plans to cut the AMS.

    Ting is also holding out for a different jaw-dropping discovery: heavy antimatter nuclei. It would be huge because antinuclei heavier than a deuteron—a proton and a neutron—cannot be made in cosmic ray interactions and would have to originate in some region of the universe dominated by antimatter. Ting claims the AMS has captured a few antihelium nuclei [Science]. Coutu says a mountain of evidence already proves no antimatter regions exist, so the unpublished signals must be spurious, perhaps produced by misidentified helium nuclei.

    The antimatter claim, too, may remain untested. Despite last year’s reprieve, the AMS faces an uncertain future. Pumps that cool key detector components need replacing, and the fix will require a spacewalk, scheduled for October. “It’s no big deal,” Ting says, although he won’t guarantee success.

    If the AMS stops working, it will leave behind an outstanding legacy, even if it’s not the one Ting envisions. The detector has collected exquisite data on cosmic rays such as nuclei of helium, boron, beryllium, and carbon. The data are helping scientists understand what produces these ordinary cosmic rays, and how they journey through space. “The cosmic ray data that they’re producing is fantastic,” says Tarlé, often a vocal critic of Ting. “It wouldn’t have been done if Sam hadn’t convinced DOE and NASA to do it.”

    See the full article here .


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  • richardmitnick 10:25 am on January 25, 2019 Permalink | Reply
    Tags: , , , , , , Science Magazine   

    From Science Magazine: “Missions expose surprising differences in the interiors of Saturn and Jupiter” 

    AAAS
    From Science Magazine

    Jan. 17, 2019
    Paul Voosen

    1
    Material thousands of kilometers below the clouds of Jupiter and Saturn tugs subtly on orbiting spacecraft, revealing hidden structure and motions.
    NASA/JPL/Space Science Institute.

    A clever use of radio signals from planetary spacecraft is allowing researchers to pierce the swirling clouds that hide the interiors of Jupiter and Saturn, where crushing pressure transforms matter into states unknown on Earth. The effort, led by Luciano Iess of Sapienza University in Rome, turned signals from two NASA probes, Cassini at Saturn and Juno at Jupiter, into probes of gravitational variations that originate deep inside these gas giants.

    What the researchers have found is fueling a high-stakes game of compare and contrast. The results, published last year in Nature for Jupiter and this week in Science for Saturn, show that “the two planets are more complex than we thought,” says Ravit Helled, a planetary scientist at the University of Zurich in Switzerland. “Giant planets are not simple balls of hydrogen and helium.”

    In the 1980s, Iess helped pioneer a radio instrument for Cassini that delivered an exceptionally clear signal because it worked in the Ka band, which is relatively free of noise from interplanetary plasma. By monitoring fluctuations in the signal, the team planned to search for gravitational waves from the cosmos and test general relativity during the spacecraft’s journey to Saturn, which began in 1997. Iess’s group put a similar device on Juno, which launched in 2011, but this time the aim was to study Jupiter’s interior.

    Juno skims close to Jupiter’s surface every 53 days, and with each pass hidden influences inside the planet exert a minute pull on the spacecraft, resulting in tiny Doppler shifts in its radio signals. Initially, Iess and his team thought measuring those shifts wouldn’t be feasible at Saturn because of the gravitational influence of its rings. But that obstacle disappeared earlier this decade, after the Cassini team decided to end the mission by sending the craft on a series of orbits, dubbed the Grand Finale, that dipped below the rings and eliminated their effects. As a result, Iess and colleagues could use radio fluctuations to map the shape of gravity fields at both planets, allowing them to infer the density and movements of material deep inside.

    One goal was to probe the roots of the powerful winds that whip clouds on the gas giants into distinct horizontal bands. Scientists assumed the winds would either be shallow, like winds on Earth, or very deep, penetrating tens of thousands of kilometers into the planets, where extreme pressure is expected to rip the electrons from hydrogen, turning it into a metallike conductor. The results for Jupiter were a puzzle: The 500-kilometer-per-hour winds aren’t shallow, but they reach just 3000 kilometers into the planet, some 4% of its radius. Saturn then delivered a different mystery: Despite its smaller volume, its surface winds, which top out at 1800 kilometers per hour, go three times deeper, to at least 9000 kilometers. “Everybody was caught by surprise,” Iess says.

    Scientists think the explanation for both findings lies in the planets’ deep magnetic fields. At pressures of about 100,000 times that of Earth’s atmosphere—well short of those that create metallic hydrogen—hydrogen partially ionizes, turning it into a semiconductor. That allows the magnetic field to control the movement of the material, preventing it from crossing the field lines. “The magnetic field freezes the flow,” and the planet becomes rigid, says Yohai Kaspi, a planetary scientist at the Weizmann Institute of Science in Rehovot, Israel, who worked with Iess. Jupiter has three times Saturn’s mass, which causes a far more rapid increase in atmospheric pressure—about three times faster. “It’s basically the same result,” says Kaspi, but the rigidity sets in at a shallower depth.

    The Juno and Cassini data yield only faint clues about greater depths. Scientists once believed the gas giants formed much like Earth, building up a rocky core before vacuuming gas from the protoplanetary disc. Such a stately process would have likely led to distinct layers, including a discrete core enriched in heavier elements. But Juno’s measurements, interpreted through models, suggested Jupiter’s core has only a fuzzy boundary, its heavy elements tapering off for up to half its radius. This suggests that rather than forming a rocky core and then adding gas, Jupiter might have taken shape from vaporized rock and gas right from the start, says Nadine Nettelmann, a planetary scientist at the University of Rostock in Germany.

    The picture is still murkier for Saturn. Cassini data hint that its core could have a mass of some 15 to 18 times that of Earth, with a higher concentration of heavy elements than Jupiter’s, which could suggest a clearer boundary. But that interpretation is tentative, says David Stevenson, a planetary scientist at the California Institute of Technology in Pasadena and a co-investigator on Juno. What’s more, Cassini was tugged by something deep within Saturn that could not be explained by the winds, Iess says. “We call it the dark side of Saturn’s gravity.” Whatever is causing this tug, Stevenson adds, it’s not found on Jupiter. “It is a major result. I don’t think we understand it yet.”

    Because Cassini’s mission ended with the Grand Finale, which culminated with the probe’s destruction in Saturn’s atmosphere, “There’s not going to be a better measurement anytime soon,” says Chris Mankovich, a planetary scientist at the University of California, Santa Cruz. But although the rings complicated the gravity measurements, they also offer an opportunity. For some unknown reason—perhaps its winds, perhaps the pull of its many moons—Saturn vibrates. The gravitational influence of those oscillations minutely warps the shape of its rings into a pattern like the spiraling arms of a galaxy. The result is a visible record of the vibrations, like the trace on a seismograph, which scientists can decipher to plumb the planet. Mankovich says it’s clear that some of these vibrations reach the deep interior, and he has already used “ring seismology” to estimate how fast Saturn’s interior rotates.

    Cassini’s last gift may be to show how fortunate scientists are to have the rings as probes. Data from the spacecraft’s final orbits enabled Iess’s team to show the rings are low in mass, which means they must be young, as little as 10 million years old—otherwise, encroaching interplanetary soot would have darkened them. They continue to rain material onto Saturn, the Cassini team has found, which could one day lead to their demise. But for now they stand brilliant against the gas giant, with more stories to tell.

    See the full article here .


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  • richardmitnick 1:42 pm on January 2, 2019 Permalink | Reply
    Tags: , , , , Breathtaking touchdown, , , Science Magazine   

    From Science Magazine: “Japan’s asteroid mission faces ‘breathtaking’ touchdown” 

    AAAS
    From Science Magazine

    Jan. 2, 2019
    Dennis Normile

    1
    Hayabusa2 imaged its shadow during a rehearsal descent. JAXA

    JAXA/Hayabusa 2 Credit: JAXA/Akihiro Ikeshita

    Japan’s Hayabusa mission made history in 2010 for bringing back to Earth the first samples ever collected on an asteroid. But the 7-year, 4-billion-kilometer odyssey was marked by degraded solar panels, innumerable mechanical failures, and a fuel explosion that knocked the spacecraft into a tumble and cut communications with ground control for 2 months. When planning its encore, Hayabusa2, Japan’s scientists and engineers were determined to avoid such drama. They made components more robust, enhanced communications capabilities, and thoroughly tested new technologies.

    But the target asteroid, Ryugu, had fresh surprises in store. “By looking at the details of every asteroid ever studied, we had expected to find at least some wide flat area suitable for a landing,” says Yuichi Tsuda, Hayabusa2’s project manager at the Japan Aerospace Exploration Agency’s Institute of Space and Astronautical Science (ISAS), which is headquartered in Sagamihara. Instead, when the spacecraft reached Ryugu in June 2018—at 290 million kilometers from Earth—it found a cragged, cratered, boulder-strewn surface that makes landing a daunting challenge. The first sampling touchdown, scheduled for October, was postponed until at least the end of this month, and at a symposium here on 21 and 22 December, ISAS engineers presented an audacious new plan to make a pinpoint landing between closely spaced boulders. “It’s breathtaking,” says Bruce Damer, an origins of life researcher at the University of California, Santa Cruz.

    Yet most everything else has gone according to plan since Hayabusa2 was launched in December 2014. Its cameras and detectors have already provided clues to the asteroid’s mass, density, and mineral and elemental composition, and three rovers dropped on the asteroid have examined the surface. At the symposium, ISAS researchers presented early results, including evidence of an abundance of organic material and hints that the asteroid’s parent body once held water. Those findings “add to the evidence that asteroids rather than comets brought water and organic materials to Earth,” says project scientist Seiichiro Watanabe of Nagoya University in Japan.

    Ryugu is 1 kilometer across and 900 meters top to bottom, with a notable bulge around the equator, like a diamond. Visible light observations and computer modeling suggest it’s a porous pile of rubble that likely agglomerated dust, rocks, and boulders after another asteroid or planetesimal slammed into its parent body during the early days of the solar system. Ryugu spins around its own axis once every 7.6 hours, but simulations suggest that during the early phase of its formation, it had a rotation period of only 3.5 hours. That probably produced the bulge, by causing surface landslides or pushing material outward from the core, Watanabe says. Analyzing surface material from the equator in an Earth-based laboratory could offer support for one of those scenarios, he adds. If the sample has been exposed to space weathering for a long time, it was likely moved there by landslides; if it is relatively fresh, it probably migrated from the asteroid’s interior.

    So far, Hayabusa2 has not detected water on or near Ryugu’s surface. But its infrared spectrometer has found signs of hydroxide-bearing minerals that suggest water once existed either on the parent body or on the asteroid, says Mutsumi Komatsu, a planetary materials scientist at the Graduate University for Advanced Studies in Hayama, Japan. The asteroid’s high porosity also suggests it once harbored significant amounts of water or ice and other volatile compounds that later escaped, Watanabe says. Asteroids such as Ryugu are rich in carbon as well, and they may have been responsible for bringing both water and carbon, life’s key building block, to a rocky Earth early in its history. (Comets, by contrast, are just 3% to 5% carbon.)

    Support for that theory, known as the late heavy bombardment, comes from another asteroid sample return mission now in progress. Early last month, NASA’s OSIRISREx reached asteroid Bennu, which is shaped like a spinning top as well and, the U.S. space agency has reported, has water trapped in the soil. “We’re lucky to be able to conduct comparative studies of these two asteroid brothers,” Watanabe says.

    Geologist Stephen Mojzsis of the University of Colorado in Boulder is not convinced such asteroids will prove to be the source of Earth’s water; there are other theories, he says, including the possibility that a giant Jupiter-like gaseous planet migrated from the outer to the inner solar system, bringing water and other molecules with it around the time Earth was formed. Still, findings on Ryugu’s shape and composition “scientifically, could be very important,” he says.

    Some new details come from up-close looks at the asteroid’s surface. On 21 September, Hayabusa2 dropped a pair of rovers the size of a birthday cake, named Minerva-II1A and -II1B, on Ryugu’s northern hemisphere. Taking advantage of its low gravity to hop autonomously, they take pictures that have revealed “microscopic features of the surface,” Tsuda says. And on 5 October, Hayabusa2 released a rover developed by the German and French space agencies that analyzed soil samples in situ and returned additional pictures.

    The ultimate objective, to bring asteroid samples back to Earth, will allow lab studies that can reveal much more about the asteroid’s age and content. ISAS engineers programmed the craft to perform autonomous landings, anticipating safe touchdown zones at least 100 meters in diameter. Instead, the biggest safe area within the first landing zone turned out to be just 12 meters wide.

    That will complicate what was already a nail-biting operation. Prior to each landing, Hayabusa2 planned to drop a small sphere sheathed in a highly reflective material to be used as a target, to ensure the craft is moving in sync with the asteroid’s rotation. Gravity then pulls the craft down gently until a collection horn extending from its underside makes contact with the asteroid; after a bulletlike projectile is fired into the surface, soil and rock fragments hopefully ricochet into a catcher within the horn. For safety, the craft has to steer clear of rocks larger than 70 centimeters.

    During a rehearsal in late October, Hayabusa2 released a target marker above the 12-meter safe circle; unfortunately, it came to rest more than 10 meters outside the zone. But it is just 2.9 meters away from the edge of a second possible landing site that’s 6 meters in diameter. Engineers now plan to have the craft first hover above the target marker and then move laterally to be above the center of one of the two sites. Because the navigation camera points straight down, the target marker will be outside the camera’s field of view as Hayabusa2 descends, leaving the craft to navigate on its own.

    “We are now in the process of selecting which landing site” to aim for, says Fuyuto Terui, who is in charge of mission guidance, navigation, and control. Aiming at the smaller zone means Hayabusa2 can keep the target marker in sight until the craft is close to the surface; the bigger zone gives more leeway for error, but the craft will lose its view of the marker earlier in the descent.

    Assuming the craft survives the first landing, plans call for Hayabusa2 to blast a 2-meter-deep crater into Ryugu’s surface at another site a few months later, by hitting it with a 2-kilogram, copper projectile. This is expected to expose subsurface material for observations by the craft’s cameras and sensors; the spacecraft may collect some material from the crater as well, using the same horn device. There could be a third touchdown, elsewhere on the asteroid. If all goes well, Hayabusa2 will make it back to Earth with its treasures in 2020.

    See the full article here .


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  • richardmitnick 12:14 pm on December 19, 2018 Permalink | Reply
    Tags: , Discovery of recent Antarctic ice sheet collapse raises fears of a new global flood, , Glaciologists worry about the present-day stability of the West Antarctic Ice Sheet, Science Magazine   

    From Science Magazine: “Discovery of recent Antarctic ice sheet collapse raises fears of a new global flood” 

    AAAS
    From Science Magazine

    Dec. 18, 2018
    Paul Voosen

    1
    A 30-kilometer crack angles across the Pine Island Glacier, a vulnerable part of the West Antarctic Ice Sheet. NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team/Flickr

    Some 125,000 years ago, during the last brief warm period between ice ages, Earth was awash. Temperatures during this time, called the Eemian, were barely higher than in today’s greenhouse-warmed world. Yet proxy records show sea levels were 6 to 9 meters higher than they are today, drowning huge swaths of what is now dry land.

    Scientists have now identified the source of all that water: a collapse of the West Antarctic Ice Sheet. Glaciologists worry about the present-day stability of this formidable ice mass. Its base lies below sea level, at risk of being undermined by warming ocean waters, and glaciers fringing it are retreating fast. The discovery, teased out of a sediment core and reported last week at a meeting of the American Geophysical Union in Washington, D.C., validates those concerns, providing evidence that the ice sheet disappeared in the recent geological past under climate conditions similar to today’s. “We had an absence of evidence,” says Anders Carlson, a glacial geologist at Oregon State University in Corvallis, who led the work. “I think we have evidence of absence now.”

    If it holds up, the finding would confirm that “the West Antarctic Ice Sheet might not need a huge nudge to budge,” says Jeremy Shakun, a paleoclimatologist at Boston College. That, in turn, suggests “the big uptick in mass loss observed there in the past decade or two is perhaps the start of that process rather than a short-term blip.” If so, the world may need to prepare for sea level to rise farther and faster than expected: Once the ancient ice sheet collapse got going, some records suggest, ocean waters rose as fast as some 2.5 meters per century.

    As an analogy for the present, the Eemian, from 129,000 to 116,000 years ago, is “probably the best there is, but it’s not great,” says Jacqueline Austermann, a geophysicist at Columbia University’s Lamont-Doherty Earth Observatory. Global temperatures were some 2°C above preindustrial levels (compared with 1°C today). But the cause of the warming was not greenhouse gases, but slight changes in Earth’s orbit and spin axis, and Antarctica was probably cooler than today. What drove the sea level rise, recorded by fossil corals now marooned well above high tide, has been a mystery.

    Scientists once blamed the melting of Greenland’s ice sheet. But in 2011, Carlson and colleagues exonerated Greenland after identifying isotopic fingerprints of its bedrock in sediment from an ocean core drilled off its southern tip. The isotopes showed ice continued to grind away at the bedrock through the Eemian. If the Greenland Ice Sheet didn’t vanish and push up sea level, the vulnerable West Antarctic Ice Sheet was the obvious suspect. But the suspicion rested on little more than simple subtraction, Shakun says. “It’s not exactly the most compelling or satisfying argument.”

    Carlson and his team set out to apply their isotope technique to Antarctica. First, they drew on archived marine sediment cores drilled from along the edge of the western ice sheet. Studying 29 cores, they identified geochemical signatures for three different bedrock source regions: the mountainous Antarctic Peninsula; the Amundsen province, close to the Ross Sea; and the area in between, around the particularly vulnerable Pine Island Glacier.

    Armed with these fingerprints, Carlson’s team then analyzed marine sediments from a single archived core, drilled farther offshore in the Bellingshausen Sea, west of the Antarctic Peninsula. A stable current runs along the West Antarctic continental shelf, picking up ice-eroded silt along the way. The current dumps much of this silt near the core’s site, where it builds up fast and traps shelled microorganisms called foraminifera, which can be dated by comparing their oxygen isotope ratios to those in cores with known dates. Over a stretch of 10 meters, the core contained 140,000 years of built-up silt.

    For most of that period, the silt contained geochemical signatures from all three of the West Antarctic bedrock regions, the team reported, suggesting continuous ice-driven erosion. But in a section dated to the early Eemian, the fingerprints winked out: first from the Pine Island Glacier, then from the Amundsen province. That left only silt from the mountainous peninsula, where glaciers may have persisted. “We don’t see any sediments coming from the much larger West Antarctic Ice Sheet, which we’d interpret to mean that it was gone. It didn’t have that erosive power anymore,” Carlson says.

    He concedes that the dating of the core is not precise, which means the pause in erosion may not have taken place during the Eemian. It is also possible that the pause itself is illusory—that ocean currents temporarily shifted, sweeping silt to another site.

    More certainty is on the way. Next month, the International Ocean Discovery Program’s JOIDES Resolution research ship will begin a 3-month voyage to drill at least five marine cores off West Antarctica.

    2
    JOIDES Resolution research ship

    “That’s going to be a great test,” Carlson says. Meanwhile, he hopes to get his own study published in time to be included in the next United Nations climate report. In the 2001 and 2007 reports, West Antarctic collapse was not even considered in estimates of future sea level; only in 2013 did authors start to talk about an Antarctic surprise, he says. Research is due by December 2019. “We gotta beat that deadline.”

    See the full article here .


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  • richardmitnick 2:51 pm on November 29, 2018 Permalink | Reply
    Tags: , , , Blazing quasars reveal the universe hit ‘peak star birth’ 3 million to 4 million years after the big bang, , Science Magazine   

    From Science Magazine: “Blazing quasars reveal the universe hit ‘peak star birth’ 3 million to 4 million years after the big bang” 

    AAAS
    From Science Magazine

    Nov. 29, 2018
    Sid Perkins

    1
    DESY/Science Communication Lab

    When were most of the universe’s stars born? Scientists have long known that the answer is “long ago.” But a new study that scrutinizes the radiation from blazing quasars suggests a far more precise answer: some 3 million to 4 billion years after the big bang.

    Blazing quasars, or “blazars,” are galaxies whose intense brightness is fueled in large part by gas, dust, and stars being sucked into the supermassive black holes that lie at their centers. Unlike most distant stars and galaxies, blazars pump out gamma rays that can be picked up by sensors on space-based observatories orbiting Earth. As material spirals inward along the plane of the galaxy’s disk, powerful beams of radiation (above) emerge along the galaxy’s rotational axis. When one of those spotlightlike beams is pointed toward Earth, the blazars appear particularly bright.

    In the new study, researchers looked at the radiation beamed toward Earth by more than 700 blazars scattered across the sky. Analyzing the blazars’ gamma ray emissions, they found that some were blocked more effectively than others. That’s significant because when photons from the gamma rays travel through space, they can interact with the low-energy photons from stars to create subatomic particles like electrons and protons. So the more gamma ray emissions blocked, the thicker the fog of photons in that part of intergalactic space—and the more stars required to make them.

    Matching the “foggy” regions up to the distance of the blazars—between 200 million and 11.6 billion light-years from Earth—the researchers were able to determine rates of star formation for those regions, accounting for more than 90% of the history of the universe, they report today in Science. Peak rates of star birth, which were about 10 times higher than today’s rates, occurred between 9.7 billion and 10.7 billion years ago.

    See the full article here .


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  • richardmitnick 4:02 pm on November 20, 2018 Permalink | Reply
    Tags: , , Norwegian REV Big Boat Big Scence, , Science Magazine   

    From Science Magazine: “Norwegian billionaire funds deluxe deep ocean research ship” 

    AAAS
    From Science Magazine

    Nov. 19, 2018
    Erik Stokstad

    1
    Twice as big as most research ships, the REV (seen in an artist’s concept) can operate in polar regions.
    ESPEN ØINO INTERNATIONAL

    “A dream vessel” is what Joana Xavier, a sponge expert at the University of Porto in Portugal, calls a new research ship due to launch in 2021. Funded by a Norwegian billionaire, the 183-meter-long Research Expedition Vessel (REV) will be the largest such ship ever built, more than twice the length of most rivals. Engineered to endure polar ice, punishing weather, and around-the-world voyages, the REV will not only be big and tough, but packed with top-of-the-line research gear—and luxurious accommodations. Its full capabilities were detailed for the first time last week at a meeting on deep-sea exploration at The Royal Society in London.

    The $350 million ship, under construction in a Black Sea shipyard in Romania, is owned by Kjell Inge Røkke, 60, who made his fortune in fishing, offshore oil, and other marine industries. In October, he promised an additional $150 million to REV Ocean in Fornebu, Norway, to operate the ship for at least 3 years, giving scientists free access. Røkke started the foundation last year to find solutions to climate change, ocean acidification, overfishing, and marine pollution. “The scale of the investment and commitment is astounding,” says Victor Zykov, science director of the Schmidt Ocean Institute, a charity in Palo Alto, California, that has its own research vessel, the Falkor.

    Many national research fleets are aging and shrinking. Since 2005, for example, the U.S. academic fleet has declined from 27 vessels to 18, and by 2025 it will it drop to 16 ships. As a result, marine scientists can face long waits for ship time. “If I want to know what’s happening in a particular place, it might not work out within a decade,” says Antje Boetius, an oceanographer and director of the Alfred Wegener Institute in Bremerhaven, Germany. Philanthropists have launched several vessels to help shorten the queue, but few are dedicated to research, and all are dwarfed by the REV.

    It offers room for 60 researchers and large areas for science and engineering. It will have trawls for capturing marine life and a remotely operated vehicle (ROV) for on-the-spot observations, a rare combination, and much else. “The idea that all the assets are on the ship, and you can pick and choose, that is tremendous,” says Ajit Subramaniam, a microbial oceanographer at the Lamont-Doherty Earth Observatory of Columbia University. The ROV, capable of 6000-meter descents, can be launched through large side doors or a moon pool in the hull. A pair of ship-borne helicopters can release smaller autonomous underwater vehicles (AUVs), which don’t need tethers to the main vessel. “Think of it as an aircraft carrier for robotics,” says Chris German, a marine geochemist at Woods Hole Oceanographic Institution in Massachusetts. The REV will also have a crewed submersible, probably one capable of descending 2000 meters.

    The main trawl, designed by Røkke’s company Aker BioMarine for harvesting krill in the Southern Ocean, can remain 3000 meters deep while funneling fish to a tube that quickly pumps them up to the ship’s wet labs. This offers the tantalizing possibility of collecting jellyfish and other soft organisms that normally don’t survive the slow trip to the surface when the trawl is winched up, opening a porthole into marine food webs. “If the gear can sample with less damage, this would really help,” says biological oceanographer Xabier Irigoien, science director of AZTI, a nonprofit institute for marine research in Pasaia, Spain.

    The REV could also make a significant contribution to understanding fisheries on the high seas, Irigoien adds. The intergovernmental organizations that regulate fishing beyond national jurisdictions don’t own ships and can rarely afford to pay for time. Free access to the REV could help scientists fill the gaps. They might be able to track tagged tuna or sharks with AUVs, for instance, while sizing up schools of fish with the ship’s high-tech sonar. By combining data from the trawl and sonar, Irigoien says, researchers could chart potential fisheries in the deep sea before they’re exploited. The same technologies would be useful for investigating far-flung marine protected areas.

    Norwegian REV Big Boat Big Scence

    Most research vessels are spartan, but on the REV scientists will have nearly full run of the ship, including its lounges, gym, dining room, and seven-story atrium. Magne Furuholmen, an artist and former keyboardist of 1980s pop group A-ha, is choosing the art collection. The REV is also eco-friendly: It’s fuel efficient with low emissions and a broad, stable hull designed to reduce noise pollution. If it encounters a garbage patch, booms can collect up to 5 tons a day of plastic to incinerate onboard for energy.

    Alex Rogers, an oceanographer at the University of Oxford in the United Kingdom, starts next month as the full-time science director for REV Ocean. He says scheduling an expedition on the REV could be quicker and more flexible than on government research vessels, which are sometimes limited by range, budget, or scientific focus. On the other hand, working with philanthropists is not like dealing with a research funding agency. “You have to explain what you’re doing,” Rogers says. “Be prepared to communicate with them.”

    Røkke’s history could raise concerns about hidden agendas. “I think there will always be some level of suspicion from the public that a person like Røkke—who made a fortune in ocean industries—that somehow there are strings attached,” Rogers admits. So he is working with the Research Council of Norway to design an independent review process that will select projects for ship time. Rogers says the only expectation is that researchers focus on solutions and share their data after they publish. “If Alex is involved, I have faith,” says Kerry Howell, a deep-sea ecologist at the University of Plymouth in the United Kingdom. “He’s not the kind of person who would work for the dark side.”

    As for Røkke, he has no plans to run the foundation and is “very meticulous about this being fully independent and objective,” says Nina Jensen, CEO of REV Ocean. “He is serious about making a difference for the oceans.” Jensen, who studied marine biology and previously led the environmental advocacy group WWF Norway , says she told Røkke she will resign if one of his companies, Aker BP, drills for oil in Norway’s Lofoten islands, which boast rich fisheries and the largest known deep-water coral reefs.

    To help cover the costs of operation, for 4 months a year the REV will open 60% of its berths on research expeditions to paying eco-tourists. For another 4 months, the entire ship will be available as a luxury yacht. Jensen hopes benefactors will charter it as a “floating think tank” to win more support for ocean protection. Any extra funds raised will go to support early-career scientists.

    It’s an unproven model, Jensen concedes, but the REV won’t sink or float on its fundraising prowess. Røkke’s pledge last month to support operations was only his first, Jensen says. “It will not be the last.”

    See the full article here .


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  • richardmitnick 7:17 pm on November 15, 2018 Permalink | Reply
    Tags: "Younger Dryas" cooling event, , , , Hiawatha Glacier, Hidden beneath Hiawatha is a 31-kilometer-wide impact crater big enough to swallow Washington D.C., Massive crater under Greenland’s ice points to climate-altering impact in the time of humans, Science Magazine   

    From Science Magazine: “Massive crater under Greenland’s ice points to climate-altering impact in the time of humans” 

    AAAS
    From Science Magazine

    1
    A 1.5-kilometer asteroid, intact or in pieces, may have smashed into an ice sheet just 13,000 years ago.
    NASA SCIENTIFIC VISUALIZATION STUDIO

    Nov. 14, 2018
    Paul Voosen

    On a bright July day 2 years ago, Kurt Kjær was in a helicopter flying over northwest Greenland—an expanse of ice, sheer white and sparkling. Soon, his target came into view: Hiawatha Glacier, a slow-moving sheet of ice more than a kilometer thick. It advances on the Arctic Ocean not in a straight wall, but in a conspicuous semicircle, as though spilling out of a basin. Kjær, a geologist at the Natural History Museum of Denmark in Copenhagen, suspected the glacier was hiding an explosive secret. The helicopter landed near the surging river that drains the glacier, sweeping out rocks from beneath it. Kjær had 18 hours to find the mineral crystals that would confirm his suspicions.

    What he brought home clinched the case for a grand discovery. Hidden beneath Hiawatha is a 31-kilometer-wide impact crater, big enough to swallow Washington, D.C., Kjær and 21 co-authors report today in a paper in Science Advances. The crater was left when an iron asteroid 1.5 kilometers across slammed into Earth, possibly within the past 100,000 years.

    Though not as cataclysmic as the dinosaur-killing Chicxulub impact, which carved out a 200-kilometer-wide crater in Mexico about 66 million years ago, the Hiawatha impactor, too, may have left an imprint on the planet’s history.

    6
    Artist’s reconstruction of Chicxulub crater soon after impact, 66 million years ago.
    DETLEV VAN RAVENSWAAY/SCIENCE SOURCE

    The timing is still up for debate, but some researchers on the discovery team believe the asteroid struck at a crucial moment: roughly 13,000 years ago, just as the world was thawing from the last ice age. That would mean it crashed into Earth when mammoths and other megafauna were in decline and people were spreading across North America.

    The impact would have been a spectacle for anyone within 500 kilometers. A white fireball four times larger and three times brighter than the sun would have streaked across the sky. If the object struck an ice sheet, it would have tunneled through to the bedrock, vaporizing water and stone alike in a flash. The resulting explosion packed the energy of 700 1-megaton nuclear bombs, and even an observer hundreds of kilometers away would have experienced a buffeting shock wave, a monstrous thunder-clap, and hurricane-force winds. Later, rock debris might have rained down on North America and Europe, and the released steam, a greenhouse gas, could have locally warmed Greenland, melting even more ice.

    The news of the impact discovery has reawakened an old debate among scientists who study ancient climate. A massive impact on the ice sheet would have sent meltwater pouring into the Atlantic Ocean—potentially disrupting the conveyor belt of ocean currents and causing temperatures to plunge, especially in the Northern Hemisphere. “What would it mean for species or life at the time? It’s a huge open question,” says Jennifer Marlon, a paleoclimatologist at Yale University.

    A decade ago, a small group of scientists proposed a similar scenario [Science]. They were trying to explain a cooling event, more than 1000 years long, called the Younger Dryas, which began 12,800 years ago, as the last ice age was ending. Their controversial solution was to invoke an extraterrestrial agent: the impact of one or more comets. The researchers proposed that besides changing the plumbing of the North Atlantic, the impact also ignited wildfires across two continents that led to the extinction of large mammals and the disappearance of the mammoth-hunting Clovis people of North America. The research group marshaled suggestive but inconclusive evidence, and few other scientists were convinced. But the idea caught the public’s imagination despite an obvious limitation: No one could find an impact crater.

    Proponents of a Younger Dryas impact now feel vindicated. “I’d unequivocally predict that this crater is the same age as the Younger Dryas,” says James Kennett, a marine geologist at the University of California, Santa Barbara, one of the idea’s original boosters.

    But Jay Melosh, an impact crater expert at Purdue University in West Lafayette, Indiana, doubts the strike was so recent. Statistically, impacts the size of Hiawatha occur only every few million years, he says, and so the chance of one just 13,000 years ago is small. No matter who is right, the discovery will give ammunition to Younger Dryas impact theorists—and will turn the Hiawatha impactor into another type of projectile. “This is a hot potato,” Melosh tells Science. “You’re aware you’re going to set off a firestorm?”

    It started with a hole. In 2015, Kjær and a colleague were studying a new map of the hidden contours under Greenland’s ice. Based on variations in the ice’s depth and surface flow patterns, the map offered a coarse suggestion of the bedrock topography—including the hint of a hole under Hiawatha.

    Kjær recalled a massive iron meteorite in his museum’s courtyard, near where he parks his bicycle. Called Agpalilik, Inuit for “the Man,” the 20-ton rock is a fragment of an even larger meteorite, the Cape York, found in pieces on northwest Greenland by Western explorers but long used by Inuit people as a source of iron for harpoon tips and tools. Kjær wondered whether the meteorite might be a remnant of an impactor that dug the circular feature under Hiawatha. But he still wasn’t confident that it was an impact crater. He needed to see it more clearly with radar, which can penetrate ice and reflect off bedrock.

    Kjær’s team began to work with Joseph MacGregor, a glaciologist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who dug up archival radar data. MacGregor found that NASA aircraft often flew over the site on their way to survey Arctic sea ice, and the instruments were sometimes turned on, in test mode, on the way out. “That was pretty glorious,” MacGregor says.

    The radar pictures more clearly showed what looked like the rim of a crater, but they were still too fuzzy in the middle. Many features on Earth’s surface, such as volcanic calderas, can masquerade as circles. But only impact craters contain central peaks and peak rings, which form at the center of a newborn crater when—like the splash of a stone in a pond—molten rock rebounds just after a strike. To look for those features, the researchers needed a dedicated radar mission.

    Coincidentally, the Alfred Wegener Institute for Polar and Marine Research in Bremerhaven, Germany, had just purchased a next-generation ice-penetrating radar to mount across the wings and body of their Basler aircraft, a twin-propeller retrofitted DC-3 that’s a workhorse of Arctic science. But they also needed financing and a base close to Hiawatha.

    Kjær took care of the money. Traditional funding agencies would be too slow, or prone to leaking their idea, he thought. So he petitioned Copenhagen’s Carlsberg Foundation, which uses profits from its global beer sales to finance science. MacGregor, for his part, enlisted NASA colleagues to persuade the U.S. military to let them work out of Thule Air Base, a Cold War outpost on northern Greenland, where German members of the team had been trying to get permission to work for 20 years. “I had retired, very serious German scientists sending me happy-face emojis,” MacGregor says.

    2
    NASA and German aircraft used radar to see the contours of an impact crater beneath the ice of Hiawatha Glacier. JOHN SONNTAG/NASA

    Three flights, in May 2016, added 1600 kilometers of fresh data from dozens of transits across the ice—and evidence that Kjær, MacGregor, and their team were onto something. The radar revealed five prominent bumps in the crater’s center, indicating a central peak rising some 50 meters high. And in a sign of a recent impact, the crater bottom is exceptionally jagged. If the asteroid had struck earlier than 100,000 years ago, when the area was ice free, erosion from melting ice farther inland would have scoured the crater smooth, MacGregor says. The radar signals also showed that the deep layers of ice were jumbled up—another sign of a recent impact. The oddly disturbed patterns, MacGregor says, suggest “the ice sheet hasn’t equilibrated with the presence of this impact crater.”

    But the team wanted direct evidence to overcome the skepticism they knew would greet a claim for a massive young crater, one that seemed to defy the odds of how often large impacts happen. And that’s why Kjær found himself, on that bright July day in 2016, frenetically sampling rocks all along the crescent of terrain encircling Hiawatha’s face. His most crucial stop was in the middle of the semicircle, near the river, where he collected sediments that appeared to have come from the glacier’s interior. It was hectic, he says—”one of those days when you just check your samples, fall on the bed, and don’t rise for some time.”

    In that outwash, Kjær’s team closed its case. Sifting through the sand, Adam Garde, a geologist at the Geological Survey of Denmark and Greenland in Copenhagen, found glass grains forged at temperatures higher than a volcanic eruption can generate. More important, he discovered shocked crystals of quartz. The crystals contained a distinctive banded pattern that can be formed only in the intense pressures of extraterrestrial impacts or nuclear weapons. The quartz makes the case, Melosh says. “It looks pretty good. All the evidence is pretty compelling.”

    Now, the team needs to figure out exactly when the collision occurred and how it affected the planet.

    The Younger Dryas, named after a small white and yellow arctic flower that flourished during the cold snap, has long fascinated scientists. Until human-driven global warming set in, that period reigned as one of the sharpest recent swings in temperature on Earth. As the last ice age waned, about 12,800 years ago, temperatures in parts of the Northern Hemisphere plunged by as much as 8°C, all the way back to ice age readings. They stayed that way for more than 1000 years, turning advancing forest back into tundra.

    The trigger could have been a disruption in the conveyor belt of ocean currents, including the Gulf Stream that carries heat northward from the tropics. In a 1989 paper in Nature, Kennett, along with Wallace Broecker, a climate scientist at Columbia University’s Lamont-Doherty Earth Observatory, and others, laid out how meltwater from retreating ice sheets could have shut down the conveyor. As warm water from the tropics travels north at the surface, it cools while evaporation makes it saltier. Both factors boost the water’s density until it sinks into the abyss, helping to drive the conveyor. Adding a pulse of less-dense freshwater could hit the brakes. Paleoclimate researchers have largely endorsed the idea, although evidence for such a flood has been lacking until recently.

    Then, in 2007, Kennett suggested a new trigger. He teamed up with scientists led by Richard Firestone, a physicist at Lawrence Berkeley National Laboratory in California, who proposed a comet strike at the key moment [PNAS]. Exploding over the ice sheet covering North America, the comet or comets would have tossed light-blocking dust into the sky, cooling the region. Farther south, fiery projectiles would have set forests alight, producing soot that deepened the gloom and the cooling. The impact also could have destabilized ice and unleashed meltwater that would have disrupted the Atlantic circulation.

    The climate chaos, the team suggested, could explain why the Clovis settlements emptied and the megafauna vanished soon afterward. But the evidence was scanty. Firestone and his colleagues flagged thin sediment layers at dozens of archaeological sites in North America. Those sediments seemed to contain geochemical traces of an extraterrestrial impact, such as a peak in iridium, the exotic element that helped cement the case for a Chicxulub impact. The layers also yielded tiny beads of glass and iron—possible meteoritic debris—and heavy loads of soot and charcoal, indicating fires.

    The team met immediate criticism. The decline of mammoths, giant sloths, and other species had started well before the Younger Dryas. In addition, no sign existed of a human die-off in North America, archaeologists said. The nomadic Clovis people wouldn’t have stayed long in any site. The distinctive spear points that marked their presence probably vanished not because the people died out, but rather because those weapons were no longer useful once the mammoths waned, says Vance Holliday, an archaeologist at The University of Arizona in Tucson. The impact hypothesis was trying to solve problems that didn’t need solving.

    The geochemical evidence also began to erode. Outside scientists could not detect the iridium spike in the group’s samples. The beads were real, but they were abundant across many geological times, and soot and charcoal did not seem to spike at the time of the Younger Dryas. “They listed all these things that aren’t quite sufficient,” says Stein Jacobsen, a geochemist at Harvard University who studies craters.

    Yet the impact hypothesis never quite died. Its proponents continued to study the putative debris layer at other sites in Europe and the Middle East. They also reported finding microscopic diamonds at different sites that, they say, could have been formed only by an impact. (Outside researchers question the claims of diamonds.)

    Now, with the discovery of Hiawatha crater, “I think we have the smoking gun,” says Wendy Wolbach, a geochemist at De-Paul University in Chicago, Illinois, who has done work on fires during the era.

    The impact would have melted 1500 gigatons of ice, the team estimates—about as much ice as Antarctica has lost because of global warming in the past decade. The local greenhouse effect from the released steam and the residual heat in the crater rock would have added more melt. Much of that freshwater could have ended up in the nearby Labrador Sea, a primary site pumping the Atlantic Ocean’s overturning circulation. “That potentially could perturb the circulation,” says Sophia Hines, a marine paleoclimatologist at Lamont-Doherty.

    Leery of the earlier controversy, Kjær won’t endorse that scenario. “I’m not putting myself in front of that bandwagon,” he says. But in drafts of the paper, he admits, the team explicitly called out a possible connection between the Hiawatha impact and the Younger Dryas.

    4
    Banded patterns in the mineral quartz are diagnostic of shock waves from an extraterrestrial impact. ADAM GARDE, GEUS

    The evidence starts with the ice. In the radar images, grit from distant volcanic eruptions makes some of the boundaries between seasonal layers stand out as bright reflections. Those bright layers can be matched to the same layers of grit in cataloged, dated ice cores from other parts of Greenland [Science]. Using that technique, Kjær’s team found that most ice in Hiawatha is perfectly layered through the past 11,700 years. But in the older, disturbed ice below, the bright reflections disappear. Tracing the deep layers, the team matched the jumble with debris-rich surface ice on Hiawatha’s edge that was previously dated to 12,800 years ago. “It was pretty self-consistent that the ice flow was heavily disturbed at or prior to the Younger Dryas,” MacGregor says.

    Other lines of evidence also suggest Hiawatha could be the Younger Dryas impact [PNAS]. In 2013, Jacobsen examined an ice core from the center of Greenland, 1000 kilometers away. He was expecting to put the Younger Dryas impact theory to rest by showing that, 12,800 years ago, levels of metals that asteroid impacts tend to spread did not spike. Instead, he found a peak in platinum, similar to ones measured in samples from the crater site. “That suggests a connection to the Younger Dryas right there,” Jacobsen says.

    For Broecker, the coincidences add up. He had first been intrigued by the Firestone paper, but quickly joined the ranks of naysayers. Advocates of the Younger Dryas impact pinned too much on it, he says: the fires, the extinction of the megafauna, the abandonment of the Clovis sites. “They put a bad shine on it.” But the platinum peak Jacobsen found, followed by the discovery of Hiawatha, has made him believe again. “It’s got to be the same thing,” he says.

    Yet no one can be sure of the timing. The disturbed layers could reflect nothing more than normal stresses deep in the ice sheet. “We know all too well that older ice can be lost by shearing or melting at the base,” says Jeff Severinghaus, a paleoclimatologist at the Scripps Institution of Oceanography in San Diego, California. Richard Alley, a glaciologist at Pennsylvania State University in University Park, believes the impact is much older than 100,000 years and that a subglacial lake can explain the odd textures near the base of the ice. “The ice flow over growing and shrinking lakes interacting with rough topography might have produced fairly complex structures,” Alley says.

    A recent impact should also have left its mark in the half-dozen deep ice cores drilled at other sites on Greenland, which document the 100,000 years of the current ice sheet’s history. Yet none exhibits the thin layer of rubble that a Hiawatha-size strike should have kicked up. “You really ought to see something,” Severinghaus says.

    Brandon Johnson, a planetary scientist at Brown University, isn’t so sure. After seeing a draft of the study, Johnson, who models impacts on icy moons such as Europa and Enceladus, used his code to recreate an asteroid impact on a thick ice sheet. An impact digs a crater with a central peak like the one seen at Hiawatha, he found, but the ice suppresses the spread of rocky debris. “Initial results are that it goes a lot less far,” Johnson says.

    5
    In 2016, Kurt Kjær looked for evidence of an impact in sand washed out from underneath Hiawatha Glacier. He would find glassy beads and shocked crystals of quartz.
    SVEND FUNDER

    Even if the asteroid struck at the right moment, it might not have unleashed all the disasters envisioned by proponents of the Younger Dryas impact. “It’s too small and too far away to kill off the Pleistocene mammals in the continental United States,” Melosh says. And how a strike could spark flames in such a cold, barren region is hard to see. “I can’t imagine how something like this impact in this location could have caused massive fires in North America,” Marlon says.

    It might not even have triggered the Younger Dryas. Ocean sediment cores show no trace of a surge of freshwater into the Labrador Sea from Greenland, says Lloyd Keigwin, a paleoclimatologist at the Woods Hole Oceanographic Institution in Massachusetts. The best recent evidence, he adds, suggests a flood into the Arctic Ocean through western Canada instead [Nature Geoscience].

    An external trigger may be unnecessary in any case, Alley says. During the last ice age, the North Atlantic saw 25 other cooling spells, probably triggered by disruptions to the Atlantic’s overturning circulation. None of those spells, known as Dansgaard-Oeschger (D-O) events, was as severe as the Younger Dryas, but their frequency suggests an internal cycle played a role in the Younger Dryas, too. Even Broecker agrees that the impact was not the ultimate cause of the cooling. If D-O events represent abrupt transitions between two regular states of the ocean, he says, “you could say the ocean was approaching instability and somehow this event knocked it over.”

    Still, Hiawatha’s full story will come down to its age. Even an exposed impact crater can be a challenge for dating, which requires capturing the moment when the impact altered existing rocks—not the original age of the impactor or its target. Kjær’s team has been trying. They fired lasers at the glassy spherules to release argon for dating, but the samples were too contaminated. The researchers are inspecting a blue crystal of the mineral apatite for lines left by the decay of uranium, but it’s a long shot. The team also found traces of carbon in other samples, which might someday yield a date, Kjær says. But the ultimate answer may require drilling through the ice to the crater floor, to rock that melted in the impact, resetting its radioactive clock. With large enough samples, researchers should be able to pin down Hiawatha’s age.

    Given the remote location, a drilling expedition to the hole at the top of the world would be costly. But an understanding of recent climate history—and what a giant impact can do to the planet—is at stake. “Somebody’s got to go drill in there,” Keigwin says. “That’s all there is to it.”

    See the full article here .


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